Parallel guides



\March 4, 1958 P. F. BOE-HM PARALLEL GUIDES Filed Feb. 25, 1955 INVENTOR.

United States PatentO PARALLEL GUIDES Paul F. Boehm, Flushing, N. Y. Application February 25, 1955', Serial No. 490,671 2 Claims. 01. 33-30 The present invention refers to drafting equipment, and more specifically to means forguiding a straightedge or equivalent thereof over the drawing surface in such a manner that it remains parallel to itself during such movement. For thesake of briefness such means will be called parallel guides in this specification and in the pertaining claims.

It is an object of this invention to provide a parallel guide which is reliable and easy 'to handle, yet, cornparatively simple to manufacture.

It is a further object of the invention to provide a parallel guide which can be mounted onthe top surface of the drawing'board without any parts attached. to the lower surface thereof so that a board equipped with such a guide can be laid fiat on a disk or table without interference with any other object present thereon, and without {the danger of damaging the table surface.

It is anotherobject of'the invention to provide a parallel guide that can be mounted on any portion of 'a largedrawing' board in connection with a straightedge substantially; shorter than the width of the board so that p'apers orbooks" or drafting tools may be kept on'those areas of the boardwhichare not covered bythe move: ment ofthe straightedge equipped with the-parallel guide according to the invention. 4

It is still another object of the invention to provide a parallel guide which can be mounted on the drawing board in the fsimplestlpossible nianrier',.even with a few thumbtacks, and therefore can be, similarly removed, if desiredgwithout'anytrouble.

Further,;objec'ts"and advantages ofthe parallel guide according to the invention willfbecorne; apparent: from tlie'following' description of two preferred embodiments thereof, reference being had to the accompanying drawing, in which Fig. 1 is an axonometric illustration of a drawing board equipped with a straightedge and parallel guide according to the invention;

Fig. 2 is an elevation, and Fig. 3 is the corresponding plan view of the essential drive portion of the parallel guide;

Fig. 4 shows certain details of Fig. 2 at a larger scale, and

Fig. 5 is a plan view showing another embodiment of the invention.

Fig. 1 shows a drawing board 10 and a straightedge 11 in a position parallel with the front edge of the board 10. The straightedge 11 is somewhat shorter than the said front-edge, and is free to move parallel with itself over the top surface of the board 10. Near the outer ends of straightedge 11 bearing blocks 12 are mounted so as to accommodate a shaft 13 that extends over the whole length of the straightedge 11 and may rotate in the said bearing blocks 12. The outer ends of shaft 13 extend each beyond the particular bearing block 12 and carry each a sprocket 14 firmly attached to the shaft 13.

Mounted on top of the board 10 are two racks 15,

,7 2,825,139 Patented Mar. 4, 1958 ice spaced apart from each other by the same distanceas the sprockets 1'4 and extending at right angles-to the shaft 13'. If the sprockets 14 are kept in.engagernent with said racks 15 ,then the shaft and the straightedge 11 can be moved towards and from the front edgeof board 10 only in parallelism with itself.

Actually, the racks 15 could be any type, of conventional racks provided the teeth of the racks match those of, the,sprockets andprovided the racks are attached to the board. I However, this would not serve all the purposes of the invention, as will be' explaiuedlater. Therefore, I" have selected as the most convenient and advantageous type of rack the tapes or so-called fchains of conventional slide-fasteners or fzippersff I have found that the consecutive row of ,solid'pieces or prongs assembled along th e reinforced edge of a flexible strip of materiall'ca n be'used in connection with standard sprockets of proper pitch; in exactly the same manner as rigid racks.

Fig. 4 shows, in cross-section, the lower portion of a sprocket 1 4. The zipper chain consists of the flexible strip or tape 15b with a reinforced edge which is solidly embraced by the metalelementor prong 15a. The tooth 14 of the sprocket penetrates between the consecutive prongs 15a and thus engages with the zipper like it would do with a regular solid rack. V I Figs. 2 and 3 illustrate the essential parts of the sprocket-rack combination. Most of the parts in ques tion have been described above. It remains therefore, only to refer to themeans required for maintaining the mutual engagement'of sprocket 14 and rack 15. If the assembly of straightedge 11 with hearing blocks 12, shaft 13 and sprockets 1'4 were merely restingwith' its sprockets 14 on: the racks consisting of the zipper v tapes 15 as shown in Figs. 1, 3 and 4, Withthe teeth 14' of-the said sprockets in engagement with the prong s' 15qof'said tapes, "then this engagement would only exist as long as the said assemblyis held down by'gravity' or by pressure applied by the; user; It could easily happenl that the'spr ockets jump the tracks; Topreveu t this and to ensure Pe m e n em n a uiqemem er1655 attached to thetbearing block- 12;, possibly with inter p i' i p a a s c a anner. anwhea the, rack-strip 15- is extended tautlythe prongs 15a are 1 kept in prope r engagement with sprocket ld; I As shown clear 1y y. F g zrguae. mem ers ex en s. P r el w th; and underneath, tape 15 leaving justl enough spacehetween its upper r i e j adi th,$ 1aqkt.: at. he; pron'gs 15d may keep engaged with saidj sproc b cannot get out of engagement while the sprocket f4 is rolling over the track tape 15. The bent-up end of guide member 16 and the spacer 17 also prevent the rack'strip 15 from moving sideways out of engagement with the sprocket 14.

In Fig. 1 the ends of rack strips 15 are attached to the surface of board 10 by clamping straps 18 which are nailed or screwed to the board. Evidently, these straps could be dispensed with, and instead the strips 15 pinned to the board simply by thumbtacks. Also, if for instance the board to which the assembly is to be attached should be narrower than the length of the straightedge 11, then appropriate brackets attached to the outer edges of board 10 might be used for mounting the strips 15 actually off the board, running along the outside edges thereof. On the other hand, it is also evident from Fig. 1 that the straightedge with the parallel guide device may be mounted on a large board leaving workspace available outside the area over which the straightedge would travel.

It will be readily understood that the use of the rack and sprocket with the connecting shaft as a parallel guide, and in particular the use of a flexible rack in the form 3 of the conventional zipper tapes results in an extremely advantageous and handy piece of equipment of great adaptability. First. of all, the ordinary zipper tapes are far less expensive than rigid racks. They are more simply attachable to the drawing board. The whole parallel guide assembly, straightedge and racks, can be shipped in its assembled state, ready foruse, because thefiexible rack strips can be wrapped around the straightedge Without difficulty or danger. The rack strips can be provided in ample length so as to allow for sufiicient movement of the straightedge even on a comparatively large board,

' because in the case of use on a smaller board the not required excess length of the strip may be left hanging over the far edge of the board. Both the last. two mentioned features are not present in the case of using solid racks.

In the example described, each rack strip 15 is actually only one-half. of a regular zipper which is known to comprise a pair of such strips interengaged with each other and separably by a so-called slider. However, while my experiments have proven this to be entirely satisfactory, it is not impossible that cases may be found in which for greatest strength a rack type consisting of a pair of strips 19a and 19b at each end of the straight 20a is stationarily mounted in the path of strips 19a, 19b.

this side of the sprockets 14a, 14b, the other slide piece 20b on the other side thereof. In this manner the strips are automatically separated on one side and reconnected on the other side of the parallel guide as the straightedge is moved one way or the other. The separation is necessary because the teeth of sprocket could not penetrate between the prongs of a closed or interlocked pair of strips for the very reason of the prongs being interlocked leaving no space between them.

It will be understood that many details of the embodiments illustrated and described could be modified without departing from the gist and scope of my invention. For instance, the mounting of the bearing blocks and their actual shape and design may be varied so as to cover the sprocket,also the shaft might be covered, the blade of the straightedge may be shortened so as not to project beyond the outer edge of the bearing block. Therefore, I do not wish to be restricted to any of the details shown and/or described as they constitute merely examples of some of the many ways how my invention could be put to practical use.

I claim:

1. A parallel guide, comprising a straightedge member adapted to be moved over a drafting surface, a shaft substantially parallel with said straightedge member, bearings attached to said straightedge member and adapted to accommodate said shaft for rotation therein, sprockets of same pitch and number of teeth solidly attached to said shaft at substantial interval, one strip of flexible material for each of said sprockets and extending at substantially right angle to said shaft, each strip being provided with a series of solid elements projecting therefrom in regular intervals so as to constitute a rack adapted to cooperate with the said sprocket, and guide means attached to said bearings and straightedge member adapted to maintain proper rack and gear engagement between said sprockets and rack strips.

2. A parallel guide, comprising a straightedge member adapted to be moved over a drafting surface, a shaft substantially parallel with said straightedge member, bearings attached to said straightedge member and adapted to accommodate said shaft for rotation therein, at least two pairs of sprockets of same pitch and number of teeth solidly attached to said shaft at substantial interval, two strips of flexible material for eachpair of said sprockets and extending at substantially right angle to said shaft, each strip being provided with a series of solid elements projecting therefrom in regular intervals so as to constitute a rack adapted to cooperate. with said sprocket, the said series of solid elements of one of a pair of strips being adapted to engage mutually and to lock said pair of strips together in the fashion of slide fastener strips, guide members attached to said bearings and. straightedge member and adapted to keep each series of solid elements in operative engagement with one of said sprockets, and means provided on said guide members adapted to separate and to join the interlockable series of solid elements of each pair of strips when the said straightedge member, shaft and sprocket assembly is moved in relation to said strips so that said flexible strips are separated while engaging said sprockets individually, but are joined in pairs in the portions outside or beyond said guide means.

References Cited in the file of this patent UNITED STATES PATENTS 832,909 Homans Oct. 9, 1906 1,185,439 Sampson May 30, 1916 2,353,086 Schaaff July 4, 1944 2,568,358 Nahmens Sept. 18, 1951 

